1. Field of the Invention
Hard and soft wheats require different milling procedures, and each class has acquired its own specific marketing niche based upon its end-use characteristics. Knowing the wheat class is important to the milling operation and for formulating appropriate marketing strategies. Present methods for classifying wheat as hard or soft are based upon color, shape, and other visual grain characteristics traditionally associated with the type. With the introduction of newer varieties, correlation between visual and end-use characteristics is not so distinct.
Bulk hardness measurements have been used as one approach to classifying wheat samples as hard or soft. However, bulk hardness measurements do not provide information as to whether or not wheats of different hardness have been mixed. Without a means for estimating product uniformity, grade determinations are difficult.
This invention relates to an apparatus and method useful for evaluating individual kernels of grain for hardness, and optionally for moisture content and grain size. The apparatus and method permit accurate classification and quality grading of grain without strict reliance upon its visual characteristics. The invention would be especially useful to grain inspectors of the Federal Grain Inspection Service (FGIS) for the grading of wheat and also for the purpose of assessing variability of hardness within a sample.
2. Description of the Prior Art
The current industry standard for determining wheat hardness is the American Association of Cereal Chemists (AACC) Method 39-70 (1983) employing near-infrared reflectance (NIR). In accord with this method, the NIR of sample wheat is compared to that of a series of reference wheats available through FGIS. Though this method effectively discriminates one class of wheat from another, the NIR instrumentation does not detect mixtures of different wheat classes.
Lai et al. [Cereal Chem. 62 (3): 178-184 (1985)] report the use of various attachments for the "Instron Universal Testing Machine" for performing compression, shear, and puncture tests on wheat samples and correlating the results with wheat hardness. Lai et al. also show a continuous automated single-kernel hardness tester referred to as the CASK-HAT. The principle of this instrument is to measure compression forces (stress) as a function of time. The device employs an in-stream pressure transducer to generate the compression force profile resulting from crushing a wheat kernel between a cam-actuated rod and a rigid anvil.
Pomeranz et al. [Cereal Chem. 65 (2): 86-94 (1988)] show a single kernel compression instrument with a semiautomated feeder for determining wheat hardness. This device was designed to crush individual kernels between two flat surfaces. The lower crushing surface is cam-driven, and the upper surface is connected to a load cell for generating data related to kernel thickness, kernel size, kernel deformation, and force to deform the kernel. The semiautomated feeder system orients each kernel with the crease downward by sliding it over action surfaces. The feeder centers the kernel under the load cell while simultaneously brushing the previously crushed kernel from the crushing surface.
Eckhoff et al., U.S. Pat. No. 4,703,647, disclose a grain hardness tester which feeds single grains into openings of a rotating plate, wherein the grains are sheared by a disc associated with a load cell and microprocessor. The microprocessor outputs a shear pattern indicative of the grain hardness.